As demand for ever-shrinking semiconductor devices continues to increase, so too will the demand for improved semiconductor wafer metrology systems. The fabrication of semiconductor devices, such as logic and memory devices, typically includes processing a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.
Metrology processes are used at various steps during a semiconductor manufacturing process to monitor and control one or more semiconductor layer processes. For example, metrology processes are used to measure one or more characteristics of a wafer such as dimension (e.g., line width, thickness, angle, etc.) of features formed on the wafer during a process step, wherein the quality of the process step can be determined by measuring the one or more characteristics. In this scenario, a given semiconductor sample may include a set of metrology targets, with film stacks or two-dimensional and three-dimensional patterned structures surrounded by one or more materials of various geometries and properties.
Spectroscopic ellipsometry (SE) metrology measurements sample the light reflected off metrology targets at different optical parameters. The SE data of metrology targets is used to determine wafer characteristics. There is a continuing need for improved SE metrology tools, for example, so that SE data for different target characteristics can be readily decoupled.